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Herein, we describe and study a new family of isostructural multifunctional metal-organic frameworks (MOFs) with the formula {[Ln

A family of hexakis-substituted [60]fullerene adducts endowed with the well-known tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand for spin-crossover (SCO) systems has been designed and synthesized. It has been experimentally and theoretically demonstrated that these molecular scaffolds are able to form polynuclear SCO complexes in solution. UV-vis and fluorescence spectroscopy studies have allowed monitoring of the formation of up to six Fe(ii)–bpp SCO complexes. In addition, DFT calculations have been performed to model the different complexation environments and simulate their electronic properties. The complexes retain SCO properties in the solid state exhibiting both thermal- and photoinduced spin transitions, as confirmed by temperature-dependent magnetic susceptibility and Raman spectroscopy measurements. The synthesis of these complexes demonstrates that [60]fullerene hexakis-adducts are excellent and versatile platforms to develop polynuclear SCO systems in which a fullerene core is surrounded by a SCO molecular shell., Polynuclear spin-crossover molecules showing both thermal and photoinduced spin transitions have been prepared using a [60]fullerene hexakis-adduct endowed with Fe(ii) complexes of tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand.

This work reports the synthesis and multifunctionality of 2D layered coordination polymers formulated as [Ln2(H3nmp)2]·xH2O (1, where Ln = Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, Er3+ and Y3+) (x = 1 to 4). We describe detailed synthesis of the materials using various methods [typical hydrothermal reaction (HT), microwave-assisted synthesis (MWAS) and one-pot method (OP)], while discussing the various crystal morphologies which can be fine tuned by varying systematically the conditions. We further explore the multifunctionality of this material by studying its heterogeneous catalytic activity in the ring opening of styrene oxide, its photoluminescence behaviour and its cytotoxicity. A conversion of 88%/100% yield at 4 h/24 h reaction respectively, with excellent selectivity towards 2-methoxy-2-phenylethanol product (100%) was observed. Photoluminescence properties of the optically-active [Eu2(H3nmp)2]·xH2O (1Eu) and the mixed-lanthanide [(Gd0.95Eu0.5)2(H3nmp)2]·xH2O (1GdEu), on the other hand, show potential use for UV-to-visible light converters, with lifetimes of 2.31 ± 0.01 and 2.61 ± 0.01 ms at ambient temperature for 1Eu and 1GdEu samples. Preliminary cytotoxic studies showed no effects on metabolic activity of both in vitro human epithelial kidney (HK-2) and human hepatocellular carcinoma (HepG2) cell lines. A reduction of NR uptake was, however, observed indicating some cytotoxic effect on lysosomal activity.

ACKNOWLEDGMENTS The authors thank SGIker of UPV/EHU and European funding (ERDF and ESF) for technical and human support as well as wish to acknowledge the terrific help of all reviewers of the present manuscript whose comments helped to improve the quality of the work., Supporting Information The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.2c00544., Funding E.E. is grateful to the Government of the Basque Country for the predoctoral fellowship and R.F.M. to the Junior Research Position CEECIND/ 00553/2017. The research contract of FF (REF-168-89-ARH/2018) is funded by national funds (OE), through FCT, in the scope of the framework contract foreseen in nos. 4, 5, and 6 of article 23 of the Decree-Law 57/2016, of 29 August, changed by Law 57/2017, of 19 July. This work was developed within the scope of the projects given by the Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/ FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-BC21, and PID2019-108028GB-C21), Gobierno Vasco/Eusko Jaurlaritza (IT1310-19 and IT1291-19), Junta de Andalucía (FQM-394), University of the Basque Country (GIU 20/028), and CICECO-Aveiro Institute of Materials (UIDB/50011/ 2020 and UIDP/50011/2020)., Herein, we describe and study a new family of isostructural multifunctional metal–organic frameworks (MOFs) with the formula {[Ln5L6(OH)3(DMF)3]·5H2O}n (where (H2L) is 3-amino-4-hydroxybenzoic acid ligand) for magnetism and photoluminescence. Interestingly, three of the materials (Dy-, Er-, and Yb-based MOFs) present single-molecule magnet (SMM) behavior derived from the magnetic anisotropy of the lanthanide ions as a consequence of the adequate electronic distribution of the coordination environment. Additionally, photoluminescence properties of the ligand in combination with Eu and Tb counterparts were studied, including the heterometallic Eu–Tb mixed MOF that shows potential as ratiometric luminescent thermometers. Finally, the porous nature of the framework allowed showing the CO2 sorption capacity., Government of the Basque Country, Junior Research Position CEECIND/ 00553/2017, National funds (OE), Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/ FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-BC21, and PID2019-108028GB-C21), Gobierno Vasco/Eusko Jaurlaritza (IT1310-19 and IT1291-19), Junta de Andalucía (FQM-394), University of the Basque Country (GIU 20/028), CICECO-Aveiro Institute of Materials (UIDB/50011/ 2020 and UIDP/50011/2020)

Porous robust materials are typically the primary selection of several industrial processes. Many of these compounds are, however, not robust enough to be used as multifunctional materials. This is typically the case of Metal-Organic Frameworks (MOFs) which rarely combine several different excellent functionalities into the same material. In this report we describe the simple acid-base postsynthetic modification of isotypical porous rare-earth-phosphonate MOFs into a truly multifunctional system, maintaining the original porosity features: [Ln(H3pptd)]·xSolvent [where Ln3+ = Y3+ (1) and (Y0.95Eu0.05)3+ (1_Eu)] are converted into [K3Ln(pptd)]·zSolvent [where Ln3+ = Y3+ (1K) and (Y0.95Eu0.05)3+ (1K_Eu)] by immersing the powder of 1 and 1_Eu into an ethanolic solution of KOH for 48 h. The K+-exchanged Eu3+-based material exhibits a considerable boost in CO2 adsorption, capable of being reused for several consecutive cycles. It can further separate C2H2 from CO2 from a complex ternary gas mixture composed of CH4, CO2, and C2H2. This high adsorption selectivity is, additionally, observed for other gaseous mixtures, such as C3H6 and C3H8, with all these results being supported by detailed theoretical calculations. The incorporation of K+ ions notably increases the electrical conductivity by 4 orders of magnitude in high relative humidity conditions. The conductivity is assumed to be predominantly protonic in nature, rendering this material as one of the best conducting MOFs reported to date. published

In this work, we used the rigid tetrapodal organic linker, [1,1&rsquo, biphenyl]-3,3&rsquo, 5,5&rsquo, tetrayltetrakis(phosphonic acid) (H8btp), for the preparation of two lanthanide&ndash, organic framework families of compounds: layered [Ln7(H5btp)4(H5.5btp)2(H6btp)2(H2O)12]∙23.5H2O∙MeOH [where Ln3+ = Eu3+ (1Eu) and Gd3+ (1Gd)], prepared using microwave-irradiation followed by slow evaporation, 3D [Ln4(H3btp)(H4btp)(H5btp)(H2O)8]∙3H2O [where Ln3+ = Ce3+ (2Ce), Pr3+ (2Pr), and Nd3+ (2Nd)], obtained from conventional hydro(solvo)thermal synthesis. It is shown that in this system, by carefully selecting the synthetic method and the metal centers, one can increase the dimensionality of the materials, also increasing structural robustness (particularly to the release of the various solvent molecules). Compound 1 is composed of 2D layers stacked on top of each other and maintained by weak &pi, &ndash, &pi, interactions, with each layer formed by discrete 1D organic cylinders stacked in a typical brick-wall-like fashion, with water molecules occupying the free space in-between cylinders. Compound 2, on the other hand, is a 3D structure with small channels filled with crystallization water molecules. A full solid-state characterization of 1 and 2 is presented (FT-IR spectroscopy, SEM microscopy, thermogravimetric studies, powder X-ray diffraction and thermodiffractometry). The photoluminescence of 1Eu was investigated.

Photoluminescent isotypical phosphonate-based metal–organic frameworks, [Ln(H5btp)]·2H2O [where Ln3+ = Tb3+ (1) or Gd3+ (2) and H8btp = [1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis(phosphonic acid)] prepared under solvo(hydro)thermal conditions exhibit a three-dimensional supramolecular structure built up from phosphonate linkers bridging Ln3+ ions. Single-crystal X-ray diffraction of 1 revealed hydrogen bonds along the a-axis between the crystallization water molecules and the phosphonate groups. The network features lozenge-shaped tubular channels with intermolecular interactions between adjacent organic ligand molecules. Crystal packing forces bring together two ligand biphenyl groups in a parallel arrangement, forming an excimer. A ratiometric luminescent thermometer operative close to room temperature was built based on the excimer and the 5D4 → 7F5 Tb3+ emissions, exhibiting a maximum relative thermal sensitivity of 1.26%·K–1 and a minimum temperature uncertainty of 0.75 K at 319 K. This performance is...

A new metal–organic framework based on the highly flexible tetraphosphonic acid linker hexamethylenediamine-N,N,N′,N′-tetrakis(methylphosphonic acid) (H8htp) is reported. [Ln2(SO4)2(H6htp)(H2O)4]·10H2O [Ln3+= Eu3+ (1), Sm3+ (2), and Gd3+ (3)] was readily obtained by microwave heating at moderate temperatures (80 °C) and low reaction time (15 min). The reaction was carried out in aqueous medium and, because of the high flexibility of the organic linker, sulfuric acid was added in small quantities. This acid delays the coordination process and blocks access of the phosphonic acid groups by coordinating the sulfate anion to the metal center, leading to the formation of a compact 3D network. Sulfuric acid further proved to be crucial for the formation of the materials because the use of different acids led to either no precipitation or amorphous compounds. When compared to the only known and reported material based on the same building blocks, this approach allowed us to significantly reduce the reaction time...

The use of a macromolecular RAFT (macro-RAFT) agent to encapsulate anisotropic nano-objects via emulsion polymerization is an emerging route to prepare polymer/inorganic colloidal nanocomposites. However, a number of requirements have to be fulfilled. This work aims at highlighting the effects of the preparative procedure and dispersion method on the amount of macro-RAFT agent adsorbed onto SiO2-coated Gd2O3:Eu3+ nanorods. The adsorption of macro-RAFT agent was studied using the depletion method with UV–vis spectrophotometry. Measurements were performed at a fixed concentration of nanorods and varying concentrations of the macro-RAFT agent in aqueous dispersion at room temperature. The adsorption isotherms showed that for the same initial macro-RAFT agent concentration, the highest adsorption capacity of the macro-RAFT agent on nanorods was usually achieved for non-calcined thin SiO2-coated nanorods under mild bath sonication.

Ln3+-bearing Metal-Organic Frameworks (MOFs) are attracting much attention because of their unique luminescence properties and the possibility of fine-tuning the metal coordination spheres by post-synthetic modification (PSM). Here, we report PSM of the well-known IRMOF-3 by reaction with methyl 3-chloro-3-oxopropanoate and pyridine-2,6-dicarbonyl dichloride affording, respectively, IRMOF-3-CM and IRMOF-3-PY. 1H NMR of the digested modified samples showed ca. 100 % conversion of the amino group. The pendant groups of PSM IRMOF-3 were subsequently used to coordinate Eu+3 and Tb3+ and the luminescence properties of the materials studied.

In this manuscript, microwave-assisted synthesis was used to prepare a new organic building block and a Metal-Organic Framework based on this unit. The tetrapodal organic linker [1,1′-biphenyl]-3,3′,5,5′-tetrayltetrakis(phosphonic acid) (H8btp) was combined with lanthanide cations affording the isotypical 2D lanthanide-organic frameworks [Ln4(H6btp)2(H4btp)2(H8btp)(H2O)16]·12H2O [where Ln3+ = La3+ (1), (La0.9Eu0.1)3+ (2) and (La0.9Tb0.1)3+ (3)]. 1 was isolated as large single-crystals and its crystal structure was solved by single-crystal X-ray diffraction. Phase identification of the Eu3+- (2) and Tb3+-based (3) materials was performed by powder X-ray diffraction. Compound 1 consists of two-dimensional double-deck layers, characterized by an unprecedented tetranodal 2,4,4,4-connected layered network, with total point symbol {4·85}2{42·84}{43·82·10}4{4}2. Supramolecular π–π interactions exist both within and between layers. 1–3 were fully characterized in the solid-state by a plethora of techniques [elemental and thermogravimetric analyses, electron microscopy (SEM and EDS), FT-IR spectroscopy and solid-state NMR]. Photoluminescence properties of the optically-active mixed-lanthanide materials 2 and 3 reveal that the employed H8−xbtp−x residues are better suited to sensitize Tb3+ than Eu3+, with the measured lifetimes being of 0.83 ± 0.01 and 0.22 ± 0.01 ms, respectively.

Tetrathiafulvalene-Lanthanide (TTF-Ln) Metal-Organic Frameworks (MOFs) are an interesting class of multifunctional materials in which porosity can be combined with electronic properties such as electrical conductivity, redox activity, luminescence and magnetism. Herein we report a new family of isostructural TTF-Ln MOFs, denoted as MUV-5(Ln) (Ln = Gd, Tb, Dy, Ho, Er), exhibiting semiconducting properties as a consequence of the short intermolecular S···S contacts established along the chain direction between partially oxidised TTF moieties. In addition, this family shows photoluminescence properties and single-molecule magnetic behaviour, finding near-infrared (NIR) photoluminescence in the Yb/Er derivative and slow relaxation of the magnetisation in the Dy and Er derivatives. As such properties are dependent on the electronic structure of the lanthanide ion, we emphasise the immense structural, electronic and functional versatility of this class of materials.

Microporous silicate Eu-AV-20 has recently proved to be a promising ion exchange material for cesium removal from aqueous solutions, and its potential for Cs+ photoluminescence sensing was additionally demonstrated. In this work, Cs+ removal was performed in a fixed-bed column, and the influence of linear velocity and mass of ion exchanger on the breakthrough curves was analysed. The experimental data were modelled on the basis of Nernst-Planck (NP) equations and with four well-known analytic models. The analytic expressions provided low errors (root mean square deviation, RMSD, between 3.20% and 6.47%); the 2-parameter NP-based model fitted the data quite well (RMSD = 6.66% for correlation and 6.54% for prediction), yielding crucial information on both the transport mechanism within the Eu-AV-20 particles, and the intrinsic dynamic behaviour of the fixed-bed ion exchange column. Taking into account that Eu-AV-20 samples loaded with different amounts of Cs+ exhibited distinct photoluminescence spectra, our results reinforce the potential of AV-20 materials for Cs+ sensing, which raises the possibility of online monitoring the ion exchange in a fixed-bed column using an optical fibre and a spectrometer. (C) 2015 Elsevier B.V. All rights reserved.

A new lanthanide silicate system, Na2 K[Ln3 Si6 O18 ] (Ln=Lu, Yb/ Er, Lu/Eu, or Lu/Yb/Er), comprising microcrystals embedded in an amorphous siliceous matrix, obtained by sintering at 1373 K a Na3 K[Ln2 Si6 O17 ]⋅3 H2 O nano-crystalline precursor, is reported. The crystal structure of these lanthanide silicates was solved from high-resolution synchrotron power X-ray diffraction data collected at 110 K, and further supported by 29 Si MAS NMR and Eu3+ luminescence. The materials crystallize in the Pī triclinic centrosymmetric space group, exhibiting a dense framework consisting of hexameric [Si6 O18 ]12- cyclosilicate units, and chains of two distinct {LnO6 } octahedra. Na2 K[(Lu0.75 Yb0.20 Er0.05 )3 Si6 O18 ] is the first example of a lanthanide silicate operative as a near-infrared ratiometric luminescent thermometer, with good sensitivity at cryogenic temperatures (

The first example of a dual-emitting luminescent thermometer based on lanthanide isophthalate exhibiting a maximum relative sensitivity of 3.26% K−1, a temperature uncertainty of 0.07 K at 35.5 K, and a repeatability >99.9% between 12 and 230 K.

An optimized microwave-assisted synthesis has been used to prepare an isotypical series of 3D Ln(3+) metal-organic frameworks (MOFs) based on residues of 2,5-pyridinedicarboxylic (pydc), namely, [Ln(2)(pydc)(3)(H2O)(2)] with Ln(3+) = Ce3+ (1), (La0.95Eu0.05)(3+) (1-LaEu), (La0.95Tb0.05)(3+) (1-LaTb), and (La0.90Eu0.05Tb0.05)(3+) (1-LaEuTb). The materials can be readily isolated as microcrystals after 1 min of reaction time at 120 degrees C. The compounds have been extensively studied in the solid state by vibrational spectroscopy (FTIR and FT-Raman), thermogravimetry, powder X-ray diffraction, elemental analysis, and electron microscopy (SEM, SEM mapping, and TEM). The structural relationships between the isolated materials and other solids reported in the literature have been investigated in detail from a structural and topological perspective with attention focused on the different connectivities of the employed organic ligand. The 3D densely packed [Ln(2)(pydc)(3)(H2O)(2)] compounds are very similar to the previously reported microporous 3D [Ce-2(pydc)(2)(Hpydc)(H2O)(2)]Cl(9 + y)H2O; layered [{Ce-2(pydc)(2)(Hpydc)(2)(H2O)(4)}2H(2)O](n) can be isolated at lower temperatures and transforms to [Ce-2(pydc)(3)(H2O)(2)] under certain experimental conditions. Compound 1 is an effective solid catalyst for the ring opening of styrene with methanol under mild reaction conditions (55 degrees C) to give 2-methoxy-2-phenylethanol in 100% selectivity and ca. 80% conversion. The mixed-lanthanide materials are effective UV-to-visible light converters (red 1-LaEu, green 1-LaTb, and orange 1-LaEuTb). The compounds have very high absolute emission quantum yields (43% for 1-LaEu and 75% for 1-LaTb) under indirect excitation of the UV ligand bands with lifetimes of 0.50 and 1.06 ms for 1-LaEu and 1-LaTb, respectively, and these properties result from effective intersystem crossing and ligand-to-metal transfer processes.

The first examples of chiral microporous rare-earth silico-germanates were obtained by isomorphous substitution of Si4+ by Ge4+ in small-pore Na-3[RESi3O9]center dot 3H(2)O (RE = Y3+, Eu3+), using hydrothermal synthesis. Single-crystal X-ray diffraction and Si-29 solid-state NMR clearly demonstrate the framework insertion of Ge4+, with preference for two of the three crystallographic T4+ sites. The isomorphous Ge4+ for Si4+ substitution originates a dispersion of the RE3+ environments, resulting in multiple and broader Eu3+ emission lines. Despite these, the main photoluminescence properties of pure Si- and Ge,Si-materials are very similar. A particularly intriguing feature is the detection, in both cases, of quasi-enantiomeric domains by selective excitation at 12 K. (C) 2012 Elsevier Inc. All rights reserved.

A series of layered double hydroxides with the hydrotalcite structure containing Mg2+ and Al3+ cations in the brucite-like layers and carbonate in the interlayer have been prepared, with different lanthanide cations (4% loading) in the brucite-like layers. The solids have been characterized by element chemical analysis, powder X-ray diffraction, thermal analysis, particle size distribution, FT-IR and UV-Vis spectroscopies and surface texture by adsorption-desorption of nitrogen at - 196 degrees C. The color and luminescent properties have been also studied. The results confirmed the hydrotalcite-type structure, without any sort of contaminating phases. The solids have been calcined at 1000 degrees C forming homogeneously dispersed mixed oxides, where the rock-salt structure of MgO and the MgAl2O4 spinet have been identified by powder X-ray diffraction, without any differentiated phase containing lanthanide ions. The samples (original and calcined) containing Tb3+ exhibited green fluorescence, detected under irradiation of 254 and 365 nm. The emission spectra showed a series of narrow lines ascribed to the Tb3+5D4 -> F-7(6-2) transitions. The decay curves monitored at 543 nm indicated the presence of a single local Tb3+ environment in the parent and calcined samples. For the calcined samples, the photoluminescence evidence supports the insertion of Tb3+ in MgAl2O4 rather than in MgO. (C) 2016 Elsevier Inc. All rights reserved.

The ion exchange of Cs+ from aqueous solutions was studied using a novel microporous lanthanide silicate with photoluminescence properties, Tb/Eu-AV-9. This mixed lanthanide silicate was prepared by hydrothermal synthesis, characterized by scanning electron microscopy, powder X-ray diffraction, and photoluminescence spectroscopy. Batch ion exchange experiments were performed at room temperature (295 K) to measure isotherm and kinetics (removal curves). The Langmuir-Freundlich equation provided a good fit to the equilibrium data. A kinetic model based on the Maxwell-Stefan equations was implemented and adjusted to the cesium removal curves, and achieved average deviation of 8.37%. The model parameters were the diffusion coefficients, while the convective mass transfer coefficient was purely estimated. The Maxwell-Stefan diffusivities for the interaction of the counter ions Cs+ and K+ with the solid exchanger were D-AS = 8.373 x 10(-15) m(2) s(-1) and D-BS = 2.795 x 10(-14) m(2) s(-1), respectively, being consistent with other values in the literature. With respect to photoluminescence studies, the differences found between the emission spectra of native and CS+-exchanged Tb/Eu-AV-9 disclosed the potential of this sorbent for qualitative/quantitative CS+ sensing purposes. (C) 2015 Elsevier B.V. All rights reserved.

An aluminum 2-aminoterephthalate based metal-organic framework (MOF) material was applied for the first time to prepare highly efficient heterogeneous catalysts in desulfurization processes. Sandwich-type [Eu(PW11O39)(2)](11-) polyoxometalate (POM) was supported on Al(III) and Cr(III) MIL-type MOFs, NH2-MIL-53(Al) and MIL-101(Cr), and extensive characterization confirmed the incorporation of the POM on the two supports. The catalytic performance of the two composite materials, POM/MIL(Al) and POM/MIL(Cr), was evaluated in the oxidative desulfurization (ODS) of a model fuel containing some of the most common refractory sulfur compounds in diesel. Both composite materials have shown to be active and robust heterogeneous catalysts for the efficient removal of the sulfur-containing compounds from the model diesel, and the influence of the solid support on the catalytic performance of the active species was further assessed. The POM/MIL(Al) revealed notable catalytic performance, since complete desulfurization was obtained after 2 h of reaction. Furthermore, this remarkable heterogeneous catalyst revealed to be stable and recyclable for various catalytic cycles.

Isostructural lanthanide organic frameworks (Me2NH2)(3)[Ln(3)(FDC)(4)(NO3)(4)]center dot 4H(2)O (Ln = Eu (1), Gd (2), Tb (3), H2FDC = 9-fluorenone-2,7-dicarboxylic acid), synthesized under solvothermal conditions, feature a Ln-O-C rod-packing 3D framework. Time-resolved luminescence studies show that in 1 the energy difference between the H2FDC triplet excited state (17794 cm(-1)) and the D-5(0) Eu3+ level (17241 cm(-1)) is small enough to allow a strong thermally activated ion-to-ligand back energy transfer. Whereas the emission of the ligand is essentially constant the D-5(0)-> F-7(2) intensity is quenched when the temperature increases from 12 to 320 K, rendering 1 the first single-lanthanide organic framework ratiometric luminescent thermometer based on ion-to-ligand back energy transfer. More importantly, this material is also the first example of a metal organic framework thermometer operative over a wide temperature range including the physiological (12-320 K), upon excitation with visible light (450 nm).

Hybrid multilayer films composed of poly(ethylenimine) and sandwich-type silicotungstates, K13[Ln(SiW11O39)2] (Ln(SiW11)2), Ln3+ = Eu, Tb, Dy, were prepared on glassy carbon electrodes, quartz and glass slides using the electrostatic LbL self-assembly method. The film build up, monitored by electronic spectroscopy, showed a regular stepwise growth indicating a strong interaction between layers. The X-ray photoelectron spectroscopy measurements corroborated the successful fabrication of the hybrid films with the PEI–POMs composition and pointed out that the intrinsic charge compensation from the film components is the major contribution, although there is some extrinsic charge compensation from the counter cations from the POMs and electrolyte. All the LbL films showed W-based reduction processes due to the immobilized POMs; voltammetric responses revealed a kinetic facilitation of the first reduction process in the immobilized Tb(SiW11)2 and Dy(SiW11)2 polyanions relatively to the free POMs and scan rate effect showed that the tungsten reduction process for all POMs is surface-confined. The photoluminescence properties of PEI/Eu(SiW11)2 multilayer films were investigated and showed the characteristic Eu3+ emission pattern.

Cubic Gd2O3:Eu3+ (0.30, 1.01, 2.78, and 4.60 mol %) nanorods with an average diameter of ca. 14 nm were synthesized at ambient pressure and mild temperature (70 °C), using a simple and cost-effective wet-chemical route. The emission-decay curves of the 5D1 and 5D0 levels, hereafter referred to as 5D1(C2) and 5D0(C2), were investigated. Although the decay time of the 5D0 level of the Eu3+ ions residing in the C2 site of cubic Gd2O3:Eu3+ nanostructures were previously reported, little is known about the rise time component in the 5D0 emission-decay curve and the energy-transfer pathways responsible for it. The 5D0(C2) rise time and the 5D1(C2) decay time exhibit similar and strong dependence on the Eu3+ concentration and temperature. The 5D1(C2) decay time matches well the rise time extracted from the rising component of the 5D0(C2) emission-decay curve. The decay time of the 5D0(C2) level (ranging from 1.4 to 2.1 ms, depending on the filing factor of the nanorods) is longer than that of the bulk counterpar...

There is a growing interest in understanding how size-dependent quantum confinement affects the photoluminescence efficiency, excited-state dynamics, energy-transfer and thermalization phenomena in nanophosphors. For lanthanide (Ln 3+ )-doped nanocrystals, despite the localized 4f states, confinement effects are induced mostly via electron-phonon interactions. In particular, the anomalous thermalization reported so far for a handful of Ln 3+ -doped nanocrystals has been rationalized by the absence of low-frequency phonon modes. This nanoconfinement may further impact on the Ln 3+ luminescence dynamics, such as phonon-assisted energy transfer or upconversion processes. Here, intriguing and unprecedented anomalous thermalization in Gd 2 O 3 :Eu 3+ and Gd 2 O 3 :Yb 3+ ,Er 3+ nanotubes, exhibiting up to one order of magnitude larger than previously reported for similar materials, is reported. This anomalous thermalization induces unexpected energy transfer from Eu 3+ C 2 to S 6 crystallographic sites, at 11 K, and 2 H 11/2 → 4 I 15/2 Er 3+ upconversion emission; it is interpreted on the basis of the discretization of the phonon density of states, easily tuned by varying the annealing temperature (923-1123 K) in the synthesis procedure, and/or the Ln 3+ concentration (0.16-6.60%).

Much is known about the photoluminescence of lanthanide-containing systems, particularly amorphous silicates or organic-inorganic hybrids and crystalline metal-organic frameworks. Comparatively, stoichiometric microporous Ln-silicates are poorly studied. Here, we report the exceptional photoluminescence of microporous AV-24, K(7)[Ln(3)Si(12)O(32)] x xH(2)O (Ln(3+) = Sm(3+), Eu(3+), Gd(3+), Tb(3+)), the first silicate possessing Ln(3+)-O-Ln(3+) dimers (inter-Ln distance ca. 3.9 A), i.e., two edge-sharing {LnO(6)} octahedra embedded in a crystalline matrix. It is totally unprecedented that in AV-24 Eu(3+)-O-Eu(3+) dimers behave like discrete entities, i.e., molecules: they (i) have a unique emission signature, with pseudopoint group symmetry (C(i)), different from the symmetry (C(1)) of each individual constituent Eu(3+) ion, and (ii) exhibit the unusually long (5)D(0) lifetime of 10.29 ms (12 K). In accord with the experimental evidence, a molecular orbital model shows that the Eu(3+)-O-Eu(3+) dimers are energetically more stable than the individual metal ions.

The hydrothermal synthesis and detailed structural characterisation of layered materials formulated as [Ln(H2cmp)] · xH2O [where H5cmp = (carboxyme thyl)iminodi(methylphosphonic acid) and x < 1; Ln3+ = Nd3+ (1) and Eu3+ (2)] are reported. Compounds were isolated as microcrystalline powders and the crystal structure of 1 was determined by ab initio methods from high-resolution synchrotron powder X-ray diffraction (PXRD) data collected at the European Synchrotron Radiation Facility (ESRF, Grenoble, France – beam lines BM01a and BM01b). The structure of 2 was refined by conventional PXRD, starting from the atomic coordinates of 1. Materials contain a single Ln3+ metal centre in highly distorted dodecahedral coordination geometry. Connectivity through H2cmp3– anionic ligands leads to undulated tapes of Ln3+ running parallel to the b-axis [closest inter-Ln distances of 4.203(3) and 4.170(3) Å for 1 and 2] which coalesce into layers, 2 ∞[Nd(H2cmp)], extended in the bc plane. The presence of a terminal protonated phosphonate group seems to induce the formation of the layers. Topologically, the structure is a 8-connected uninodal plane net, which can be further envisaged as two periodic self-penetrated (4,4) nets. The photophysical properties of the Eu3+-bearing material were studied at room temperature (with and without vacuum). The two materials have been further stud ied using thermogravimetric analysis (TGA), vibrational spectroscopy (FT-IR) and CHN elemental analyses.

The hydrothermal synthesis and structural characterization of the lanthanide silicate system [Na(6)Ln(2)Si(12)O(30).x H(2)O] (Ln=La(3+), Sm(3+), Eu(3+), Gd(3+), and Tb(3+)), named AV-21, has been reported. Structural elucidation of the Sm(3+) analogue (isomorphous with the Eu(3+), Gd(3+), and Tb(3+) frameworks) using single-crystal synchrotron X-ray diffraction and solid-state NMR spectroscopy reveal disorder in the Si(1) second coordination sphere. La-AV-21 presents a distinct framework. These materials combine microporosity and interesting photoluminescence features with structural flexibility that allows the introduction of a second or third type of lanthanide center. Room-temperature lifetime decay dynamics have been used to estimate the Ln(3+)-Ln(3+) distances and the maximum distance over which energy transfer is active. Though the majority of Ln(3+) centers occupy regular framework positions, the Ln(2) defect centers are disordered over the Na(1) sites in the pores and greatly influence the energy-transfer process, providing a unique opportunity for studying the relationship between structural disorder and photoluminescence properties in framework solids.

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A series of two-dimensional lanthanide−organic materials (LnOFs), [Ln(H3NMP)]·1.5H2O [Ln3+ = La3+ (1), Pr3+ (2), Nd3+ (3), Sm3+ (4), or Eu3+ (5); H3NMP3- is a residue of nitrilotris(methylenephosphonic acid)], has been isolated as microcrystalline powders from hydrothermal synthesis and characterized by high-resolution laboratory and synchrotron powder X-ray diffraction (PXRD), solid-state NMR, FTIR and FT Raman spectroscopies, CHN elemental analysis, thermogravimetry, scanning electron microscopy, and energy dispersive analysis of X-ray spectroscopy. The crystal structure of [Pr(H3NMP)]·1.5H2O (2) has been solved from a combined study of ab initio methods using high-resolution PXRD data and high-resolution solid-state NMR techniques performed on [La(H3NMP)]·1.5H2O (1) (13C, 15N, 31P CPMAS and 2D 1H−1H/31P HOMCOR/HETCOR). The structure contains a single lanthanide center which does not have water molecules in its first coordination sphere. This Ln3+ center acts as the node of a neutral undulated two-dimen...

Na[(Gd1-xEux)SiO4] (x = 0.01, 0.4, 1), Na[(Gd0.8Tb0.1Eu0.1)SiO4], and Na[(Gd0.9Tb0.1)SiO4] are typically prepared by hydrothermal synthesis from a mixture of lanthanide (Ln) nitrates and an alkaline Na2SiO3 solution (autoclave, 518 K, 5 d).

The hydrothermal synthesis of the novel Na[LnSiO(4)] (Ln = Gd, Eu, Tb) disordered orthorhombic system is reported. At 100 K, and above, these materials are best described in the centrosymmetric orthorhombic Pnma space group. At lower temperatures (structure solved at 30 K) the unit cell changes to body-centered with Imma symmetry. The materials exhibit unique photophysical properties, arising from both, this phase transformation, and the disorder of the Ln(3+) ions, located at a site with D-2d point symmetry. Na[(Gd0.8Eu0.1Tb0.1)SiO4] is an unprecedented case of a luminescent ratiometric thermometer based on a very stable silicate matrix. Moreover, it is the first example of an optical thermometer whose performance (viz., excellent sensitivity at cryogenic temperatures

The ion exchange of Cs+ from aqueous solutions was studied using for the first time a microporous lanthanide silicate with photoluminescence properties, Eu-AV-20. It was prepared by hydrothermal synthesis, characterized by SEM, PLS, PXRD and ICP-MS, and several batch ion exchange experiments were performed to measure isotherm and removal curves. Additional curves were measured to evaluate the competition with Na+. The results evidenced the great selectivity of Eu-AV-20 towards Cs+ since cesium removal was slightly modified even for Na+/Cs+ concentrations ratio of 190. The emission photoluminescent spectra of native and Cs+-exchanged Eu-AV-20 were also determined for the first time, and significant modifications were detected, which discloses the potential of Eu-AV-20 for Cs+ sensing purposes. The Langmuir equation provided a good fit to the equilibrium data, with average error of 5.3%, and the Maxwell-Stefan based model adopted to represent the kinetic curves (i.e., concentration versus time) achieved a deviation of 19.0%. An analysis of variance confirmed that the model was statistically significant to represent the uptake curves. The Maxwell-Stefan based model comprises three parameters, namely, the diffusion coefficients associated to the interactions of Cs+ and Eu-AV-20, Na+/K+ and Eu-AV-20, and Cs+ and Na+/K+, whose fitted values were 2.706 x 10(-15), 5.713 x 10(-15) and 9.446 x 10(-12) m(2) s(-1). Such low values evidenced that the intraparticle mass transport mechanism is surface diffusion. This fact is ascribed to the small pores of the Eu-AV-20 crystal, 5.8 x 6.8 angstrom, because the counter ions never escape from the force field of the framework co-ions, mainly due to the strong and long range nature of the electrostatic interactions. (C) 2015 Elsevier B.V.,All rights reserved.

A heterotetranuclear Na2Eu2 complex with uncommon photo-luminescence properties is reported. The complex exhibits good emission efficiency at ambient temperature, coupled with strong temperature dependence of the emission intensity and lifetime in the 273-333 K range, all of which are key features for non-contact luminescence-based thermometers capable of sensing and imaging temperatures in the physiological range.

The synthesis and structural characterization of two novel trivalent neodymium microporous silicates whose structures are reminiscent of the structure of mineral montregianite of the rhodesite group, and their infrared light-emission properties are reported. The compound KNa2Nd[Si8O19]·5H2O (1) crystallizes in the orthorhombic Pmma space group: a = 23.9016(17) Å, b = 6.9980(5) Å, c = 6.5474(5) Å. Heating 1 at 200 °C for 40 min affords a new partially dehydrated phase, KNa2Nd[Si8O19]·2.8H2O (2), also crystallizing in the orthorhombic Pmma space group: a = 23.923(4) Å, b = 6.9950(11) Å, c = 6.5474(10) Å. Compound 2 is the hydrated phase with the lowest content of water molecule reported to date in the rhodesite mineral series.

Accurate, noninvasive, and self-referenced temperature measurements at the submicrometer scale are of great interest, prompted by the ever-growing demands in the fields of nanotechnology and nanomedicine. The thermal dependence of the phosphor's luminescence provides high detection sensitivity and spatial resolution with short acquisition times in, e.g., biological fluids, strong electromagnetic fields, and fast-moving objects. Here, it is shown that nanoparticles of [(Tb0.914Eu0.086)2(PDA)3(H2O)]·2H2O (PDA = 1,4-phenylenediacetic acid), the first lanthanide–organic framework prepared by the spray-drying method, are excellent nanothermometers operating in the solid state in the 10–325 K range (quantum yield of 0.25 at 370 nm, at room temperature). Intriguingly, this system is the most sensitive cryogenic nanothermometer reported so far, combining high sensitivity (up to 5.96 ± 0.04% K−1 at 25 K), reproducibility (in excess of 99%), and low-temperature uncertainty (0.02 K at 25 K)., This work was developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. No. FCT UID /CTM /50011/2013), financed by national funds through the FCT/MEC and when applicable co-fi nanced by FEDER under the PT2020 Partnership Agreement. C.D.S.B. (SFRH/BPD/89003/2012) and D.A. (SFRH/BPD/95032/2013) thank FCT (Fundação para a Ciência e a Tecnologia) for postdoctoral grants. Z.W. also thanks the postdoctoral scholarship under the Project No. CENTRO-07-ST24-FEDER-002032. This work was also supported by the MINECO-Spain under the Project Nos. PN MAT2012-30994 and EU FP7 ERC-Co 615954. I.I. thanks the MINECO for the RyC fellowship. ICN2 acknowledges support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant No. SEV-2013-0295.

The synthesis and luminescence characterisation of microporous Tb3+- and Er3+-silicates (Na4K2Ln2Si16O38·10H2O, AV-9 materials) are reported. These solids possess a structure related to the structure of mineral montregianite and are the first examples of siliceous materials combining zeolite-like properties with X-ray induced luminescence and infrared emission. The photoluminescence (PL) integrated intensity of Tb-AV-9 is 60% of the integrated intensity of the Gd2O2S:Tb standard X-ray scintillator. The 1.54 μm emission of hydrated Er-AV-9 is strongly enhanced with dehydration at 553 K. Calcination of Er-AV-9 at 1123 K yields a glass exhibiting efficient infrared PL at room temperature. The 4 I 13/2 → 4 I 15/2 integrated intensity of dehydrated Er-AV-9 and glass samples increases by a factor of ca. 2 and 2.2, respectively, when the temperature is raised from 75 to 300 K.

Synthetic umbite microporous zirconium silicates doped with different concentrations of Eu3+ are used as phosphorus and as precursor for preparing novel luminescence dense materials, analogues of the mineral wadeite. Both zirconium silicates display a high and stable room temperature emission in the visible spectral region. The number of Stark components detected in Eu3+-doped umbite and in Eu3+-doped wadeite indicates the presence of one and two optically active Eu3+ environments, respectively. From the luminescence features, we inferred that in doped umbite Eu3+ replace K+ located in large eight-membered rings, whereas in Eu3+-doped wadeite one of the sites corresponds to an isomorphous Eu3+/K+ substitution and the other to a replacement of the Zr4+ ions.